Filling machines periodically have to be cleaned. The most primitive and time consuming method is disassembling the machine, including the filling tank, the filling unit and all the hoses, and cleaning them individually. A less primitive system is where the system is operated normally with a cleaning or rinsing solution. This has come to be known in the industry as clean-in-place. Cleaning fluids, for example, water or chemicals are generally applied to the supply tank and the filling unit is operated through the dispensing nozzle to a drain in order to flush or clean the system. Other systems have been used, wherein the output of the nozzle has been connected back to the supply tank to create a closed loop with or without an additional pump. The additional pump allows greater pressure to be applied throughout the system to clean the hoses or other connections.
These previous designs have been added to or are adaptations of the standard filling cycle and have been designed around the filling machine. Depending upon the type of filling unit, and the degree of cleanliness or sterility required, substantial modifications had to be made. To truly clean a system, all surfaces which contact the filling material must be cleaned. This requires special operation of the valves on the filling unit as well as the portions of the filling unit. Additional ports and restructuring of the piston pump or other positive placement pumps were required. As an alternative, the displacement pump had to be disassembled for cleaning. Similarly, with the inlet and outlet valving of the filling pump, special operation or disassembly was required.
Another shortcoming of the prior art clean-in-place systems was that the filling unit was designed to fill one specific product. Thus, the clean-in-place cycles of operating including time, cycle of operation and cleaning materials to be dispensed were designed for that single product. This limits the design of the machine to dispense only that product. Each material being dispensed needs a different cleaning cycle as well as different cleaning fluids.
Where the material to be filled into a container is a heavy or dense product, the diameter of the inlet to the filling unit from the supply tank is substantially greater than the diameter of the outlet. This causes uneven flow and pressures on the inlet and outlet during the intake and discharge cycles of the filling unit during cleaning. These uneven cycles do not affect the filling operation, but make cleaning of the system using the filling unit in the cleaning cycle does not produce appropriate cleaning since the cleaning fluid is not a heavy material. The operation of the filling unit at an increased speed to create the appropriate pressures and turbulence at the output of the filling unit will not create the similar turbulence or velocity at the inlet and outlet.
Another design problem of the prior art is using the product supply tank as the source of cleaning fluid. By filling the supply tank with cleaning fluid, the surfaces are covered with an appropriate depth of cleaning fluid, therefor it cannot be cleaned by the turbulence or velocity of the cleaning fluid entering the supply tank.